Glycerol trioctanoate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

4 Sep - 3 Oct 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data based on the inhibition control of a ready biodegradability study. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2008).

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg, Karlsruhe, Germany

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal wastewater treatment plant, Breisgauer Bucht, sampled on September 3rd, 2012
- Pretreatment: The activated sludge was washed twice by settling the sludge, decanting the supernatant and re-suspending the sludge in tap water
- Concentration of sludge: 30 mg dry solids per litre (dry solid of the activated sludge was 2.9 g/L by weight measurements after 2 h drying at 110 °C

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

29 d

Details on test conditions:

TEST CONDITIONS
- Composition of medium:
Solution A (per 1 liter demineralised water):
KH2PO4: 8.50 g
K2HPO4: 21.75 g
Na2HPO4 x 2 H2O: 33.40 g
NH4Cl: 0.50 g

Solution B:
CaCL2 x 2 H2O: 36.40 g

Solution C:
MgSO4 x 7 H2O: 22.50 g

Solution D:
FeCL3 x 6 H2O: 0.25 g

For the preparation of the mineral medium 10 mL of solution A is mixed with 800 mL demineralised water, 1 mL each of solutions B, C, and D are added and the volume is made up to 1L.

- Test temperature: 21 - 24 °C

TEST SYSTEM
- Culturing apparatus: Gas wash bottles (2000 mL) with lateral connecting pieces for butyl rubber septums were used as reactors. The liquid volume was fixed as 1500 mL each. Mixing was perfomred by a magnetic stirrer with 2 cm stir bars. The test item was added into the three test vessels. The reference compound was added to the three reference vessels. Reference compound and test item were added to the toxicity control vessel
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: The CO2-free air production system consits of an air compressor, three 1000 mL gas wash bottles filled with dry soda lime in series followed by one bottle filled with 0.1 M NaOH. At the end of the system is one gas wash bottle filled with demineralised water, followed by an empty one to catch any drops of condensation water. A colour change of the soda lime from white to blue indicates that the CO2 absorption capacity is depleted. The CO2-free air is passed on to an air distributor with two input and 22 output channels and through PE-tubes.
- Test performed in closed vessels due to significant volatility of test substance: yes
- Details of trap for CO2 and volatile organics if used: The CO2 produced in the reactors was absorbed in two 250 mL gas wash bottles in series filled with 200 mL 0.2 M NaOH

SAMPLING
- Sampling method: Through the lateral connecting pieces through the butyl rubber septum using 5 mL PE syringes

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 flasks
- Toxicity control: 1 flask (5.15 mL of a stock solution of 10 g/L reference substance and 46.9 mg of the test item were added into the vessel. This corresponds to a concentration of 40.1 mg/L organic carbon)
- Reference: 3 flasks (5.15 mL of a stock solution of 10 g/L sodium benzoate was added into the reference vessels. This corresponds to a concentration of 20 mg/L organic carbon)

Reference substance (positive control):

yes

Remarks:

benzoic acid, sodium salt

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 46.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: result of toxicity control from ready biodegradability test

Results with reference substance (positive control):

The reference compound sodium benzoate reached the pass level for ready biodegradability within 7 days.

Biodegradation in the toxicity control vessel reached 81.1% within 14 days.

“If in a toxicity test, containing both the test and reference substance, less than 35% degradation (based on total DOC) or less than 25% (based on total ThOD or ThCO2) occurred within 14 days, the test substance can be assumed to be inhibitory.” (OECD guideline 301)

Since more than 81% degradation occurred in the toxicity control, the substance is with high probability not toxic to aquatic microorganisms. The test item concentration in the toxicity control of 46.9 mg/L can be used as NOEC value for the toxicity to aquatic microorganisms.

Reference 2

Endpoint:

toxicity to microorganisms

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

Summary of available data used for the endpoint assessment of the target substance

Adequacy of study:

key study

Justification for type of information:

Please refer to the analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 46.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: result of toxicity control from ready biodegradability test

Remarks on result:

other: Source: CAS 85536-07-8, Cremer, 2012, CO2 evolution (Ready biodegradability in water, screening test

Additional information

Since no studies investigating the toxicity of Glycerol trioctanoate (CAS 538-23-8) to microorganisms are available, in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5, a read-across to the structurally related source substance Glycerides, C8-10 mono and di (CAS 85536-07-8) was conducted. The source substance is representative to evaluate the toxicity of the target substance to microorganisms. This read-across is justified in detail within the analogue justification in IUCLID section 13.

The target substance Glycerol trioctanoate (CAS 538-23-8) is a monoconstituent characterized by the alcohol component glycerol which is fully esterified with octanoic acid to give glycerol triesters of octanoic acid.

The source substance Glycerides, C8-10 mono and di (CAS 85536-07-8) is a UVCB substance characterized by the alcohol component glycerol and C8-10 (even numbered) fatty acids. Esterification of glycerol gives mainly mono- and diesters of C8-10 (even numbered) fatty acids.

A NOEC for Toxicity to microorganisms was derived from the toxicity control of a ready biodegradability study OECD 301B for source substance Glycerides, C8-10 mono and di (CAS 85536-07-8). If a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2017). A substance can be assumed to be non-inhibitory to aquatic microorganisms, if in the toxicity control of a ready biodegradation test, more than 25% degradation (based on total ThCO2) occurred within 14 days (OECD guideline 301). For source substance Glycerides, C8-10 mono and di (CAS 85536-07-8), a biodegradation test according to OECD guideline 301B is available (Cremer, 2012). The test includes a toxicity control, which contains 46.9 mg/L of the test item, Glycerides, C8-10 mono and di. Within 14 days, 81.1% biodegradation took place in this toxicity control clearly indicating the lack of toxic potential of Glycerides, C8-C10, mono- and di- to activated sludge microorganisms, and therefore, the test item concentration of 46.9 mg/L can be used as a NOEC.

Based on the available results from structurally related read-across substances (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that Glycerol trioctanoate (CAS 538-23-8) is non-inhibitory of aquatic microorganisms activity and further testing for this endpoint is regarded not necessary.